Coarse actuator positioning algorithm

ABSTRACT

A computer program product for positioning an actuator, according to one embodiment, includes a computer readable storage medium having program instructions embodied therewith. The computer readable storage medium is not a transitory signal per se. The program instructions are executable by a processing circuit to cause the processing circuit to perform a method that includes generating or receiving, by the processing circuit, a first value representative of a lateral position of a tape, and using, by the processing circuit, the first value to adjust a position of a coarse actuator for moving a magnetic head in response to determining that the first value is in a first range relative to a first threshold. An integrator value is used by the processing circuit to adjust the position of the coarse actuator in response to determining that the first value is in a second range relative to the first threshold.

BACKGROUND

The present invention relates to data storage systems, and moreparticularly, this invention relates to positioning a coarse actuatorbased on the lateral position of a magnetic medium.

In magnetic storage systems, magnetic transducers read data from andwrite data onto magnetic recording media. Data is written on themagnetic recording media by moving a magnetic recording transducer to aposition over the media where the data is to be stored. The magneticrecording transducer then generates a magnetic field, which encodes thedata into the magnetic media. Data is read from the media by similarlypositioning the magnetic read transducer and then sensing the magneticfield of the magnetic media. Read and write operations may beindependently synchronized with the movement of the media to ensure thatthe data can be read from and written to the desired location on themedia.

An important and continuing goal in the data storage industry is that ofincreasing the density of data stored on a medium. For tape storagesystems, that goal has led to increasing the track and linear bitdensity on recording tape, and decreasing the thickness of the magnetictape medium. However, the development of small footprint, higherperformance tape drive systems has created various problems in thedesign of a tape head assembly for use in such systems.

In a tape drive system, the drive moves the magnetic tape over thesurface of the tape head at high speed. Usually the tape head isdesigned to minimize the spacing between the head and the tape. Thespacing between the magnetic head and the magnetic tape is crucial andso goals in these systems are to have the recording gaps of thetransducers, which are the source of the magnetic recording flux in nearcontact with the tape to effect writing sharp transitions, and to havethe read elements in near contact with the tape to provide effectivecoupling of the magnetic field from the tape to the read elements.

BRIEF SUMMARY

A computer program product for positioning an actuator, according to oneembodiment, includes a computer readable storage medium having programinstructions embodied therewith. The computer readable storage medium isnot a transitory signal per se. The program instructions are executableby a processing circuit to cause the processing circuit to perform amethod that includes generating or receiving, by the processing circuit,a first value representative of a lateral position of a tape, and using,by the processing circuit, the first value to adjust a position of acoarse actuator for moving a magnetic head in response to determiningthat the first value is in a first range relative to a first threshold.An integrator value is used by the processing circuit to adjust theposition of the coarse actuator in response to determining that thefirst value is in a second range relative to the first threshold.

Various embodiments may be implemented in a magnetic data storage systemsuch as a tape drive system, which may include a magnetic head, a drivemechanism for passing a magnetic medium (e.g., recording tape) over themagnetic head, and a processing circuit (e.g., controller) electricallycoupled to the magnetic head.

Other aspects and embodiments of the present invention will becomeapparent from the following detailed description, which, when taken inconjunction with the drawings, illustrate by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a schematic diagram of a simplified tape drive systemaccording to one embodiment.

FIG. 1B is a schematic diagram of a tape cartridge according to oneembodiment.

FIG. 2 illustrates a side view of a flat-lapped, bi-directional,two-module magnetic tape head according to one embodiment.

FIG. 2A is a tape bearing surface view taken from Line 2A of FIG. 2.

FIG. 2B is a detailed view taken from Circle 2B of FIG. 2A.

FIG. 2C is a detailed view of a partial tape bearing surface of a pairof modules.

FIG. 3 is a partial tape bearing surface view of a magnetic head havinga write-read-write configuration.

FIG. 4 is a partial tape bearing surface view of a magnetic head havinga read-write-read configuration.

FIG. 5 is a side view of a magnetic tape head with three modulesaccording to one embodiment where the modules all generally lie alongabout parallel planes.

FIG. 6 is a side view of a magnetic tape head with three modules in atangent (angled) configuration.

FIG. 7 is a side view of a magnetic tape head with three modules in anoverwrap configuration.

FIGS. 8A-8C are graphs illustrating Lateral Tape Motion (LTM) phenomenafor tapes and/or cartridges according to different embodiments.

FIG. 9 is a flowchart of a method, according to one embodiment.

FIG. 10 is a flowchart of a method, according to one embodiment.

FIGS. 11A-11C are graphs illustrating the position of a magnetic headrelative to the LTM phenomena of FIGS. 8A-8C.

DETAILED DESCRIPTION

The following description is made for the purpose of illustrating thegeneral principles of the present invention and is not meant to limitthe inventive concepts claimed herein. Further, particular featuresdescribed herein can be used in combination with other describedfeatures in each of the various possible combinations and permutations.

Unless otherwise specifically defined herein, all terms are to be giventheir broadest possible interpretation including meanings implied fromthe specification as well as meanings understood by those skilled in theart and/or as defined in dictionaries, treatises, etc.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” “an” and “the” include pluralreferents unless otherwise specified.

The following description discloses several preferred embodiments ofmagnetic storage systems for positioning a coarse actuator, as well asoperation and/or component parts thereof. Various embodiments describedherein include positioning a coarse actuator based, at least in part onlateral motion of a magnetic tape. Moreover, it should be noted thatpositioning a coarse actuator as used herein also refers to the positionof a magnetic head corresponding to the coarse actuator, as will bedescribed in further detail below.

In one general embodiment, a method includes receiving a value(IntegRevAve) representative of a lateral position of a tape, comparingthe value to a first threshold, using the value to adjust a position ofa coarse actuator when the value is in a first range relative to thefirst threshold, and selectively using an integrator center value(IntegCtr) to adjust the position of the coarse actuator when the valueis in a second range relative to the first threshold.

FIG. 1A illustrates a simplified tape drive system 100 of a tape-baseddata storage system, which may be employed in the context of the presentinvention. While one specific implementation of a tape drive is shown inFIG. 1A, it should be noted that the embodiments described herein may beimplemented in the context of any type of tape drive system.

As shown, a tape supply cartridge 120 and a take-up reel 121 areprovided to support a tape 122. One or more of the reels may form partof a removable cartridge and are not necessarily part of the system 100.The tape drive, such as that illustrated in FIG. 1A, may further includedrive motor(s) to drive the tape supply cartridge 120 and the take-upreel 121 to move the tape 122 over a tape head 126 of any type. Suchhead may include an array of readers, writers, or both.

However, as the tape 122 is unwound from a supply reel (e.g., tapesupply cartridge 120), lateral motion of the tape across the magnetictape head 126 can generally be caused by a reel runout effect and/orflange shifts. The reel runout effect results from wobbles of therotational motion of a motor used to unwind the tape 122 from a supplyreel 120. Thus, the reel runout effect repeats with each rotation of thesupply reel 120, and appears sinusoidal in nature, as will be discussedin further detail below.

Moreover, flange shifts occur when a tape 122 shifts from beingpositioned against one of the supply reel's flanges to the other flangewhile being unwound threrefrom and passed across a magnetic tape head126. This generally occurs because the distance separating the flangesof the supply reel is larger than the width of the tape in thecrosstrack direction and/or the flanges themselves are tapered. Thus, asthe tape 122 is wound onto the supply reel, the tape 122 is generallypressed against one of the two flanges and may shift from beingpositioned against one flange to the other flange multiple timesthroughout the length of the tape. As a result, when the tape 122 isunwound, the shifts between flanges create large lateral shifts of thetape's position relative to the magnetic tape head 126.

Therefore, the tape drive system 100 preferably includes a mechanism(not shown) for generating a signal representative of the lateralposition of the magnetic head 126 with respect to the tape 122, e.g., anLTM signal. According to various approaches, the mechanism may includean electronic computing device, a signal generator, an arbitrarywaveform generator, a digital pattern generator, a frequency generator,etc. Moreover, the LTM signal may be used for positioning the tape head126 such that a target track of the tape is about directly below thetape head 126, e.g., for reading therefrom and/or writing thereto, aswill be described in further detail below.

Guides 125 guide the tape 122 across the tape head 126. Such tape head126 is in turn coupled to a controller 128 via a cable 130. Thecontroller 128 may be or include a processor and/or any logic forcontrolling any subsystem of the drive 100. For example, the controller128 typically controls head functions such as servo following, datawriting, data reading, etc.

With continued reference to FIG. 1A, the controller 128 may operateunder logic known in the art, as well as any logic disclosed herein. Thecontroller 128 may be coupled to a memory 136 of any known type, whichmay store instructions executable by the controller 128. Moreover, thecontroller 128 may be configured and/or programmable to perform orcontrol some or all of the methodology presented herein. Thus, thecontroller may be considered configured to perform various operations byway of logic programmed into a chip; software, firmware, or otherinstructions being available to a processor; etc. and combinationsthereof. According to one embodiment, the controller 128 may perform oneor more operations for receiving and/or processing an LTM signal, aswill be discussed in further detail below.

The cable 130 may include read/write circuits to transmit data to thehead 126 to be recorded on the tape 122 and to receive data read by thehead 126 from the tape 122. An actuator 132 controls position of thehead 126 relative to the tape 122, and may be of conventional design.The actuator 132 includes a coarse actuator 132A and a fine actuator132B. The coarse actuator 132A is configured to position the fineactuator 132B and head 126 towards a target track on the medium. Thefine actuator 132B is then used for fine track following duringoperation. Thus, as alluded to above, according to various embodimentsdescribed herein, the position of the coarse actuator and/or positioningthe coarse actuator also refers to the position of the magnetic headand/or positioning the magnetic head.

An interface 134 may also be provided for communication between the tapedrive 100 and a host (integral or external) to send and receive the dataand for controlling the operation of the tape drive 100 andcommunicating the status of the tape drive 100 to the host, all as willbe understood by those of skill in the art.

FIG. 1B illustrates an exemplary tape cartridge 150 according to oneembodiment. Such tape cartridge 150 may be used with a system such asthat shown in FIG. 1A. As shown, the tape cartridge 150 includes ahousing 152, a tape 122 in the housing 152, and a nonvolatile memory 156coupled to the housing 152. In some approaches, the nonvolatile memory156 may be embedded inside the housing 152, as shown in FIG. 1B. In moreapproaches, the nonvolatile memory 156 may be attached to the inside oroutside of the housing 152 without modification of the housing 152. Forexample, the nonvolatile memory may be embedded in a self-adhesive label154. In one preferred embodiment, the nonvolatile memory 156 may be aFlash memory device, ROM device, etc., embedded into or coupled to theinside or outside of the tape cartridge 150. The nonvolatile memory isaccessible by the tape drive and the tape operating software (the driversoftware), and/or other device.

By way of example, FIG. 2 illustrates a side view of a flat-lapped,bi-directional, two-module magnetic tape head 200 which may beimplemented in the context of the present invention. As shown, the headincludes a pair of bases 202, each equipped with a module 204, and fixedat a small angle α with respect to each other. The bases may be“U-beams” that are adhesively coupled together. Each module 204 includesa substrate 204A and a closure 204B with a thin film portion, commonlyreferred to as a “gap” in which the readers and/or writers 206 areformed. In use, a tape 208 is moved over the modules 204 along a media(tape) bearing surface 209 in the manner shown for reading and writingdata on the tape 208 using the readers and writers. The wrap angle θ ofthe tape 208 at edges going onto and exiting the flat media supportsurfaces 209 are usually between about 0.1 degree and about 3 degrees.

The substrates 204A are typically constructed of a wear resistantmaterial, such as a ceramic. The closures 204B made of the same orsimilar ceramic as the substrates 204A.

The readers and writers may be arranged in a piggyback or mergedconfiguration. An illustrative piggybacked configuration comprises a(magnetically inductive) writer transducer on top of (or below) a(magnetically shielded) reader transducer (e.g., a magnetoresistivereader, etc.), wherein the poles of the writer and the shields of thereader are generally separated. An illustrative merged configurationcomprises one reader shield in the same physical layer as one writerpole (hence, “merged”). The readers and writers may also be arranged inan interleaved configuration. Alternatively, each array of channels maybe readers or writers only. Any of these arrays may contain one or moreservo track readers for reading servo data on the medium.

FIG. 2A illustrates the tape bearing surface 209 of one of the modules204 taken from Line 2A of FIG. 2. A representative tape 208 is shown indashed lines. The module 204 is preferably long enough to be able tosupport the tape as the head steps between data bands.

In this example, the tape 208 includes 4 to 22 data bands, e.g., with 16data bands and 17 servo tracks 210, as shown in FIG. 2A on a one-halfinch wide tape 208. The data bands are defined between servo tracks 210.Each data band may include a number of data tracks, for example 1024data tracks (not shown). During read/write operations, the readersand/or writers 206 are positioned to specific track positions within oneof the data bands. Outer readers, sometimes called servo readers, readthe servo tracks 210. The servo signals are in turn used to keep thereaders and/or writers 206 aligned with a particular set of tracksduring the read/write operations.

FIG. 2B depicts a plurality of readers and/or writers 206 formed in agap 218 on the module 204 in Circle 2B of FIG. 2A. As shown, the arrayof readers and writers 206 includes, for example, 16 writers 214, 16readers 216 and two servo readers 212, though the number of elements mayvary. Illustrative embodiments include 8, 16, 32, 40, and 64 activereaders and/or writers 206 per array, and alternatively interleaveddesigns having odd numbers of reader or writers such as 17, 25, 33, etc.An illustrative embodiment includes 32 readers per array and/or 32writers per array, where the actual number of transducer elements couldbe greater, e.g., 33, 34, etc. This allows the tape to travel moreslowly, thereby reducing speed-induced tracking and mechanicaldifficulties and/or execute fewer “wraps” to fill or read the tape.While the readers and writers may be arranged in a piggybackconfiguration as shown in FIG. 2B, the readers 216 and writers 214 mayalso be arranged in an interleaved configuration. Alternatively, eacharray of readers and/or writers 206 may be readers or writers only, andthe arrays may contain one or more servo readers 212. As noted byconsidering FIGS. 2 and 2A-B together, each module 204 may include acomplementary set of readers and/or writers 206 for such things asbi-directional reading and writing, read-while-write capability,backward compatibility, etc.

FIG. 2C shows a partial tape bearing surface view of complimentarymodules of a magnetic tape head 200 according to one embodiment. In thisembodiment, each module has a plurality of read/write (R/W) pairs in apiggyback configuration formed on a common substrate 204A and anoptional electrically insulative layer 236. The writers, exemplified bythe write transducer 214 and the readers, exemplified by the readtransducer 216, are aligned parallel to an intended direction of travelof a tape medium thereacross to form an R/W pair, exemplified by the R/Wpair 222. Note that the intended direction of tape travel is sometimesreferred to herein as the direction of tape travel, and such terms maybe used interchangeable. Such direction of tape travel may be inferredfrom the design of the system, e.g., by examining the guides; observingthe actual direction of tape travel relative to the reference point;etc. Moreover, in a system operable for bi-direction reading and/orwriting, the direction of tape travel in both directions is typicallyparallel and thus both directions may be considered equivalent to eachother.

Several R/W pairs 222 may be present, such as 8, 16, 32 pairs, etc. TheR/W pairs 222 as shown are linearly aligned in a direction generallyperpendicular to a direction of tape travel thereacross. However, thepairs may also be aligned diagonally, etc. Servo readers 212 arepositioned on the outside of the array of R/W pairs, the function ofwhich is well known.

Generally, the magnetic tape medium moves in either a forward or reversedirection as indicated by arrow 220. The magnetic tape medium and headassembly 200 operate in a transducing relationship in the mannerwell-known in the art. The piggybacked MR head assembly 200 includes twothin-film modules 224 and 226 of generally identical construction.

Modules 224 and 226 are joined together with a space present betweenclosures 204B thereof (partially shown) to form a single physical unitto provide read-while-write capability by activating the writer of theleading module and reader of the trailing module aligned with the writerof the leading module parallel to the direction of tape travel relativethereto. When a module 224, 226 of a piggyback head 200 is constructed,layers are formed in the gap 218 created above an electricallyconductive substrate 204A (partially shown), e.g., of AlTiC, ingenerally the following order for the R/W pairs 222: an insulating layer236, a first shield 232 typically of an iron alloy such as NiFe (—), CZTor Al—Fe—Si (Sendust), a sensor 234 for sensing a data track on amagnetic medium, a second shield 238 typically of a nickel-iron alloy(e.g., ˜80/20 at % NiFe, also known as permalloy), first and secondwriter pole tips 228, 230, and a coil (not shown). The sensor may be ofany known type, including those based on MR, GMR, AMR, tunnelingmagnetoresistance (TMR), etc.

The first and second writer poles 228, 230 may be fabricated from highmagnetic moment materials such as ˜45/55 NiFe. Note that these materialsare provided by way of example only, and other materials may be used.Additional layers such as insulation between the shields and/or poletips and an insulation layer surrounding the sensor may be present.Illustrative materials for the insulation include alumina and otheroxides, insulative polymers, etc.

The configuration of the tape head 126 according to one embodimentincludes multiple modules, preferably three or more. In awrite-read-write (W-R-W) head, outer modules for writing flank one ormore inner modules for reading. Referring to FIG. 3, depicting a W-R-Wconfiguration, the outer modules 252, 256 each include one or morearrays of writers 260. The inner module 254 of FIG. 3 includes one ormore arrays of readers 258 in a similar configuration. Variations of amulti-module head include a R-W-R head (FIG. 4), a R-R-W head, a W-W-Rhead, etc. In yet other variations, one or more of the modules may haveread/write pairs of transducers. Moreover, more than three modules maybe present. In further approaches, two outer modules may flank two ormore inner modules, e.g., in a W-R-R-W, a R-W-W-R arrangement, etc. Forsimplicity, a W-R-W head is used primarily herein to exemplifyembodiments of the present invention. One skilled in the art apprisedwith the teachings herein will appreciate how permutations of thepresent invention would apply to configurations other than a W-R-Wconfiguration.

FIG. 5 illustrates a magnetic head 126 according to one embodiment ofthe present invention that includes first, second and third modules 302,304, 306 each having a tape bearing surface 308, 310, 312 respectively,which may be flat, contoured, etc. Note that while the term “tapebearing surface” appears to imply that the surface facing the tape 315is in physical contact with the tape bearing surface, this is notnecessarily the case. Rather, only a portion of the tape may be incontact with the tape bearing surface, constantly or intermittently,with other portions of the tape riding (or “flying”) above the tapebearing surface on a layer of air, sometimes referred to as an “airbearing”. The first module 302 will be referred to as the “leading”module as it is the first module encountered by the tape in a threemodule design for tape moving in the indicated direction. The thirdmodule 306 will be referred to as the “trailing” module. The trailingmodule follows the middle module and is the last module seen by the tapein a three module design. The leading and trailing modules 302, 306 arereferred to collectively as outer modules. Also note that the outermodules 302, 306 will alternate as leading modules, depending on thedirection of travel of the tape 315.

In one embodiment, the tape bearing surfaces 308, 310, 312 of the first,second and third modules 302, 304, 306 lie on about parallel planes(which is meant to include parallel and nearly parallel planes, e.g.,between parallel and tangential as in FIG. 6), and the tape bearingsurface 310 of the second module 304 is above the tape bearing surfaces308, 312 of the first and third modules 302, 306. As described below,this has the effect of creating the desired wrap angle α₂ of the taperelative to the tape bearing surface 310 of the second module 304.

Where the tape bearing surfaces 308, 310, 312 lie along parallel ornearly parallel yet offset planes, intuitively, the tape should peel offof the tape bearing surface 308 of the leading module 302. However, thevacuum created by the skiving edge 318 of the leading module 302 hasbeen found by experimentation to be sufficient to keep the tape adheredto the tape bearing surface 308 of the leading module 302. The trailingedge 320 of the leading module 302 (the end from which the tape leavesthe leading module 302) is the approximate reference point which definesthe wrap angle α₂ over the tape bearing surface 310 of the second module304. The tape stays in close proximity to the tape bearing surface untilclose to the trailing edge 320 of the leading module 302. Accordingly,read and/or write elements 322 may be located near the trailing edges ofthe outer modules 302, 306. These embodiments are particularly adaptedfor write-read-write applications.

A benefit of this and other embodiments described herein is that,because the outer modules 302, 306 are fixed at a determined offset fromthe second module 304, the inner wrap angle α₂ is fixed when the modules302, 304, 306 are coupled together or are otherwise fixed into a head.The inner wrap angle α₂ is approximately tan⁻¹(δ/W) where δ is theheight difference between the planes of the tape bearing surfaces 308,310 and W is the width between the opposing ends of the tape bearingsurfaces 308, 310. An illustrative inner wrap angle α₂ is in a range ofabout 0.3° to about 1.1°, though can be any angle required by thedesign.

Beneficially, the inner wrap angle α₂ on the side of the module 304receiving the tape (leading edge) will be larger than the inner wrapangle α₃ on the trailing edge, as the tape 315 rides above the trailingmodule 306. This difference is generally beneficial as a smaller α₃tends to oppose what has heretofore been a steeper exiting effectivewrap angle.

Note that the tape bearing surfaces 308, 312 of the outer modules 302,306 are positioned to achieve a negative wrap angle at the trailing edge320 of the leading module 302. This is generally beneficial in helpingto reduce friction due to contact with the trailing edge 320, providedthat proper consideration is given to the location of the crowbar regionthat forms in the tape where it peels off the head. This negative wrapangle also reduces flutter and scrubbing damage to the elements on theleading module 302. Further, at the trailing module 306, the tape 315flies over the tape bearing surface 312 so there is virtually no wear onthe elements when tape is moving in this direction. Particularly, thetape 315 entrains air and so will not significantly ride on the tapebearing surface 312 of the third module 306 (some contact may occur).This is permissible, because the leading module 302 is writing while thetrailing module 306 is idle.

Writing and reading functions are performed by different modules at anygiven time. In one embodiment, the second module 304 includes aplurality of data and optional servo readers 331 and no writers. Thefirst and third modules 302, 306 include a plurality of writers 322 andno data readers, with the exception that the outer modules 302, 306 mayinclude optional servo readers. The servo readers may be used toposition the head during reading and/or writing operations. The servoreader(s) on each module are typically located towards the end of thearray of readers or writers.

By having only readers or side by side writers and servo readers in thegap between the substrate and closure, the gap length can besubstantially reduced. Typical heads have piggybacked readers andwriters, where the writer is formed above each reader. A typical gap is20-35 microns. However, irregularities on the tape may tend to droopinto the gap and create gap erosion. Thus, the smaller the gap is thebetter. The smaller gap enabled herein exhibits fewer wear relatedproblems.

In some embodiments, the second module 304 has a closure, while thefirst and third modules 302, 306 do not have a closure. Where there isno closure, preferably a hard coating is added to the module. Onepreferred coating is diamond-like carbon (DLC).

In the embodiment shown in FIG. 5, the first, second, and third modules302, 304, 306 each have a closure 332, 334, 336, which extends the tapebearing surface of the associated module, thereby effectivelypositioning the read/write elements away from the edge of the tapebearing surface. The closure 332 on the second module 304 can be aceramic closure of a type typically found on tape heads. The closures334, 336 of the first and third modules 302, 306, however, may beshorter than the closure 332 of the second module 304 as measuredparallel to a direction of tape travel over the respective module. Thisenables positioning the modules closer together. One way to produceshorter closures 334, 336 is to lap the standard ceramic closures of thesecond module 304 an additional amount. Another way is to plate ordeposit thin film closures above the elements during thin filmprocessing. For example, a thin film closure of a hard material such asSendust or nickel-iron alloy (e.g., 45/55) can be formed on the module.

With reduced-thickness ceramic or thin film closures 334, 336 or noclosures on the outer modules 302, 306, the write-to-read gap spacingcan be reduced to less than about 1 mm, e.g., about 0.75 mm, or 50% lessthan commonly-used LTO tape head spacing. The open space between themodules 302, 304, 306 can still be set to approximately 0.5 to 0.6 mm,which in some embodiments is ideal for stabilizing tape motion over thesecond module 304.

Depending on tape tension and stiffness, it may be desirable to anglethe tape bearing surfaces of the outer modules relative to the tapebearing surface of the second module. FIG. 6 illustrates an embodimentwhere the modules 302, 304, 306 are in a tangent or nearly tangent(angled) configuration. Particularly, the tape bearing surfaces of theouter modules 302, 306 are about parallel to the tape at the desiredwrap angle α₂ of the second module 304. In other words, the planes ofthe tape bearing surfaces 308, 312 of the outer modules 302, 306 areoriented at about the desired wrap angle α₂ of the tape 315 relative tothe second module 304. The tape will also pop off of the trailing module306 in this embodiment, thereby reducing wear on the elements in thetrailing module 306. These embodiments are particularly useful forwrite-read-write applications. Additional aspects of these embodimentsare similar to those given above.

Typically, the tape wrap angles may be set about midway between theembodiments shown in FIGS. 5 and 6.

FIG. 7 illustrates an embodiment where the modules 302, 304, 306 are inan overwrap configuration. Particularly, the tape bearing surfaces 308,312 of the outer modules 302, 306 are angled slightly more than the tape315 when set at the desired wrap angle α₂ relative to the second module304. In this embodiment, the tape does not pop off of the trailingmodule, allowing it to be used for writing or reading. Accordingly, theleading and middle modules can both perform reading and/or writingfunctions while the trailing module can read any just-written data.Thus, these embodiments are preferred for write-read-write,read-write-read, and write-write-read applications. In the latterembodiments, closures should be wider than the tape canopies forensuring read capability. The wider closures may require a widergap-to-gap separation. Therefore a preferred embodiment has awrite-read-write configuration, which may use shortened closures thatthus allow closer gap-to-gap separation.

Additional aspects of the embodiments shown in FIGS. 6 and 7 are similarto those given above.

A 32 channel version of a multi-module head 126 may use cables 350having leads on the same or smaller pitch as current 16 channelpiggyback LTO modules, or alternatively the connections on the modulemay be organ-keyboarded for a 50% reduction in cable span. Over-under,writing pair unshielded cables may be used for the writers, which mayhave integrated servo readers.

The outer wrap angles α₁ may be set in the drive, such as by guides ofany type known in the art, such as adjustable rollers, slides, etc. oralternatively by outriggers, which are integral to the head. Forexample, rollers having an offset axis may be used to set the wrapangles. The offset axis creates an orbital arc of rotation, allowingprecise alignment of the wrap angle α₁.

To assemble any of the embodiments described above, conventional u-beamassembly can be used. Accordingly, the mass of the resultant head may bemaintained or even reduced relative to heads of previous generations. Inother approaches, the modules may be constructed as a unitary body.Those skilled in the art, armed with the present teachings, willappreciate that other known methods of manufacturing such heads may beadapted for use in constructing such heads.

As tape drive storage capacity continues to improve, corresponding trackdensities rapidly increase. This results in a wide variety of LTMphenomena for different tapes and/or cartridges. For example, looking toFIG. 8A, the graph 800 illustrates one phenomenon in which a taperemains laterally shifted from a magnetic head in one direction, e.g.,resulting from a flange shift as described above. The x-axis representsa number of cycles corresponding to sampling intervals used to collectthe data presented in the graph 800. The sampling intervals may betranslated into units of time by multiplying by 50 microseconds (μsec).For example, the sampling interval 1×10^4, corresponds to (50μsec)×(1×10^4)=0.5 seconds.

According to another example, the graph 810 of FIG. 8B illustratesanother phenomenon in which short stack shifts up and/or down produceLTM spikes, which may be used to determine whether the tape is stackedagainst the upper or lower flange of a tape reel as described above.Further still, some tapes and/or cartridges have spans of upper levelLTM in addition to lower level LTM. Looking to the graph 820 of FIG. 8C,some tapes and/or cartridges have combinations of upper and lower levelLTM, e.g., with fluctuating periods and/or amplitudes.

It follows that precise track following servo systems are preferablypaired with increased track densities to minimize runtime errors. Asdescribed above, some embodiments incorporate a combination of coarseand/or fine actuators for track following with a magnetic head duringoperation (e.g., see 132A, 132B of FIG. 1A respectively). Preferably,track following is able to determine the position of the tape from anLTM signal, and use a coarse actuator to position the magnetic head atabout the center of a target track despite potential lateral offset ofthe tape. Illustrative embodiments including lateral tape motion signalconditioning for coarse servo positioning are presented in coassignedU.S. patent application Ser. No. 14/157,101 to Nhan Bui et al., filedJan. 16, 2014 and titled LATERAL TAPE MOTION SIGNAL CONDITIONING, andwhich is herein incorporated by reference.

Thus, by using a coarse actuator to position the magnetic head at aboutthe center of a target track, the short stroke and high bandwidth of thefine actuator may follow the lateral transitions of the tape duringruntime, without the risk of running out of stroke. Various embodimentsdescribed herein include apparatuses and/or methods for positioning acoarse actuator based at least in part on lateral motion of a magnetictape, as will soon become apparent.

FIG. 9 depicts a flowchart of a method 900 for determining an integratorcenter value IntegCtr, in accordance with one embodiment. As an option,the present method 900 may be implemented in conjunction with featuresfrom any other embodiment listed herein, such as those described withreference to the other FIGS. In one approach, which is in no wayintended to limit the invention, a controller may be used to perform oneor more process steps of the flowchart depicted in FIG. 9. Moreover,according to an exemplary embodiment, one or more of the process stepsof method 900 may be performed by the controller 128 of FIG. 1A.

Of course, however, such method 900 and others presented herein may beused in various applications and/or in permutations which may or may notbe specifically described in the illustrative embodiments listed herein.Further, the method 900 presented herein may be used in any desiredenvironment. Thus FIG. 9 (and the other FIGS.) should be deemed toinclude any and all possible permutations.

Looking now to FIG. 9, operation 902 of method 900 includes calculatingand/or receiving a value IntegRevAve representative of a lateralposition of a tape, e.g., at a target track thereon, relative to amagnetic head (e.g., see 122, 126 of FIG. 1A respectively). The valueIntegRevAve preferably corresponds to lateral tape motion (e.g., flangeshifts and/or reel runout) of a tape towards the top or bottom flange ofa supply reel while being unwound from the supply reel (e.g., see 121 or120 of FIG. 1A depending on the direction of tape travel). Thus,according to a preferred approach, IntegRevAve is updated after eachfull rotation of a supply reel. However according to other approaches,IntegRevAve may be updated after more than one full revolution of asupply reel, e.g., after two full rotations of a supply reel. Thus,according to an exemplary embodiment which is in no way intended tolimit the invention, if a tape supply reel has 24 portions correspondingto each full revolution thereof, IntegRevAve is preferably updated after24 portions have passed, thereby corresponding to a full revolution ofthe supply reel.

According to different embodiments, the value IntegRevAve may becalculated based on a signal, e.g., from a driver circuit of a fineactuator, integrator signal from a fine actuator compensator, a tapeedge detector that optically and/or physically detects LTM, etc.Illustrative embodiments for calculating the value IntegRevAve arepresented in U.S. patent application Ser. No. 14/157,101 titled LATERALTAPE MOTION SIGNAL CONDITIONING, which has been incorporated byreference above.

Furthermore, operation 904 of method 900 includes calculating Delta,which is equal to the absolute value of the difference betweenIntegRevAve and IntegRevAvePre. IntegRevAvePre corresponds to a previousvalue of IntegRevAve, and is updated during operation 904 to the valueIntegRevAve received in operation 902 e.g., to be used in calculatingthe next Delta value. In one approach, IntegRevAvePre may be stored inmemory (e.g., a lookup table) until the next time operation 904 isreached by method 900.

According to an example, which is in no way intended to limit theinvention, a value IntegRevAve of 200 may be received in operation 902.Moreover, IntegRevAvePre may have a stored value of 250, e.g., from thelast value IntegRevAve. Thus, still referring to the present example,Delta would be calculated as the absolute value of 200-250, whichresults in a value of 50. Furthermore, the value of IntegRevAvePre isupdated to 200 (the current value of IntegRevAve) and stored in memoryfor future use.

Referring again to FIG. 9, decision 906 of method 900 includes comparingthe value of Delta to 100. If Delta is greater than or equal to somevalue, 100 in this example, method 900 returns to operation 902, e.g.,until another value IntegRevAve is received. However, if Delta is lessthan 100, method 900 proceeds to decision 908.

According to different embodiments, Delta may be compared to a valuedifferent than 100, e.g., depending on user preference, sensitivity ofthe data, a system's margin for error, etc. Moreover, it should be notedthat in various embodiments described herein, if a decision is madedepending on a value being below a given threshold, the samedetermination may be made equivalently if the value is above thethreshold with signs reversed. For example, which is in no way intendedto limit the invention, 3>1 may produce the same determination as −3<−1.

Referring still to method 900 of FIG. 9, in decision 908, IntegRevAve iscompared to zero. If IntegCtr is greater than zero, method 900 moves tooperation 910 where IntegTop is calculated as:IntegTop=(IntegRevAve+IntegRevAvePre)/2. See operation 910. IntegTopcorresponds to the tape being positioned towards a first flange of asupply reel.

However, if IntegCtr is less than zero, method 900 moves to operation912 where IntegBot is calculated as:IntegBot=(IntegRevAve+IntegRevAvePre)/2. See operation 912. IntegBotcorresponds to the tape being positioned towards a second flange of asupply reel opposite the first flange. IntegTop and/or IntegBot mayfurther be stored in memory, e.g., for future use, depending on thedesired embodiment.

With continued reference to FIG. 9, method 900 proceeds to decision 914where IntegTop and IntegBot are compared to zero. If it is determinedthat IntegTop is not greater than zero and/or IntegBot is not less thanzero, then method 900 returns to operation 902, e.g., until anothervalue IntegRevAve is received. However, if it is determined thatIntegTop is greater than zero and that IntegBot is less than zero,method 900 proceeds to operation 916 where IntegCtr is calculated as:IntegCtr=(IntegTop+IntegBot)/2.

The integrator center value IntegCtr represents the running (e.g.,updated) sample mean of the data (e.g., signal) corresponding toIntegRevAve. According to an exemplary embodiment, the integrator centervalue IntegCtr may assist in positioning a coarse actuator to compensatefor lateral motion of a magnetic tape, as will soon become apparent.Moreover, it should be noted that “data” as used herein may includedigital and/or analog data, which may be represented by a signal, avalue or values, etc. Therefore, although in some embodiments data maybe presented as a graph, in other embodiments data may correspond todigital and/or analog data stored in a lookup table, presented to auser, etc.

FIG. 10 depicts a flowchart of a method 1000 for positioning a coarseactuator in accordance with one embodiment. As an option, the presentmethod 1000 may be implemented in conjunction with features from anyother embodiment listed herein, such as those described with referenceto the other FIGS. In one approach, which is in no way intended to limitthe invention, a controller may be used to perform one or more processsteps of the flowchart depicted in FIG. 10. Moreover, according to anexemplary embodiment, one or more of the process steps of method 1000may be performed by the controller 128 of FIG. 1A.

Looking now to FIG. 10, operation 1002 of method 1000 includes receivinga value IntegRevAve representative of a lateral position of a tape(e.g., at a target track thereon) relative to a magnetic head (e.g., see122, 126 of FIG. 1A respectively). The value IntegRevAve preferablycorresponds to lateral tape motion (e.g., flange shifts and/or reelrunout) of a tape being unwound from the supply reel. According todifferent embodiments, the value may be calculated based on a signal,e.g., from a driver circuit of a fine actuator, integrator signal from afine actuator compensator, a tape edge detector that optically and/orphysically detects LTM, etc.

Furthermore, the method 1000 includes comparing an absolute value of thevalue IntegRevAve to a first threshold threshold1, as illustrated indecision 1004. Decision 1004 determines if the lateral position of atape relative to a magnetic head is within a first threshold threshold1to direct the flowchart of method 1000 through one of the two feedbackcontrol paths illustrated.

Referring still to decision 1004, if the absolute value of IntegRevAveis in a first range relative to the first threshold threshold1 (i.e.,the absolute value of IntegRevAve is larger than threshold1), the method1000 includes using the value IntegRevAve to adjust a position of acoarse actuator. Moreover, when the absolute value of IntegRevAve is ina second range relative to the first threshold threshold1 (i.e., theabsolute value of IntegRevAve is smaller than threshold1), the method1000 includes selectively using an integrator center value IntegCtr toadjust the position of the coarse actuator, as will be described infurther detail below. Referring to the present description, “selectivelyusing” is intended to mean that in some approaches, a further decisionis performed to determine whether to adjust the coarse actuator.However, in other approaches, “selectively using” may be intended tomean that the coarse actuator is always adjusted.

As mentioned immediately above, when the absolute value of IntegRevAveis larger than the first threshold threshold1, the method 1000 includesusing the value IntegRevAve to adjust a position of a coarse actuator.According to a specific embodiment, decision 1006 of the method 1000includes comparing the value IntegRevAve to some value, in this example,zero.

If IntegRevAve is greater than zero, the current position of themagnetic head Current_step is decremented 1 step. See operation 1008.However, if IntegRevAve is less than zero, the current position of themagnetic head Current_step is incremented 1 step. See operation 1010.

By decrementing or incrementing the current position of the magnetichead as seen in operations 1008, 1010 respectively, the magnetic head ispreferably moved in the same direction as the lateral tape motion. Thus,the magnetic head may be repositioned such that the distance separatingthe current position of the magnetic head and an average position of atarget track on the laterally shifted tape (e.g., represented by theupdated value of IntegRevAve) is less than the first thresholdthreshold1.

Depending on the desired embodiment, the first threshold threshold1 mayinclude any predetermined value. According to an exemplary approach, thefirst threshold threshold1 is 3000, but may be higher or lower in otherembodiments. Moreover, in various approaches, the threshold1 may changebefore, after, and/or during an operation, e.g., depending on operationconditions; user preferences; read and/or write characteristics, e.g.,data sensitivity, operation type, etc.; etc.

Furthermore, the size of the step by which the current position of themagnetic head Current_step is incremented and decremented may includeany predetermined value. However, in some approaches the size of thestep may be determined by a device used to position the magnetic head inrelation to the tape. According to one example, a stepper motor may beused to position the magnetic head. Thus, depending on the size,functionality, design, etc. of the stepper motor, each position,selectable by stepping, may correspond to a different value. It shouldbe noted that for purposes of the present embodiment illustrated in themethod 1000 of FIG. 10, the operations correspond to a stepper motorwhich changes the position of the magnetic head by 145 counts for eachstep. For example, if it is determined in decision 1006 that the valueof IntegRevAve is greater than zero, the current position of the coarseactuator Current_step is incremented 145 counts. Moreover, otherembodiments described herein may include a coarse actuator that changesthe position of the magnetic head by 145 counts for each step.

With continued reference to FIG. 10, the method 1000 further includessetting IntegTop, IntegBot and IntegCtr to zero. See operation 1012.Moreover, after operation 1012 has been performed, the method 1000revisits operation 1002, where an updated value IntegRevAve is receivedand recompared to the first threshold threshold1 in decision 1004.

As mentioned above, if it is determined in decision 1004 that theabsolute value of the value IntegRevAve is not greater than the firstthreshold threshold1, the method 1000 includes selectively using anintegrator center value IntegCtr to adjust the position of the coarseactuator. As described above, the integrator center value IntegCtrrepresents the running (e.g., updated) sample mean of the signalcorresponding to the value IntegRevAve, and may be calculated usingmethod 900 of FIG. 9.

Looking to decision 1014 of FIG. 10, the absolute value of theintegrator center value IntegCtr is compared to a second thresholdthreshold2. If the absolute value of the integrator center valueIntegCtr is smaller than the second threshold threshold2, the lateralposition of the tape relative to the magnetic head is within an overalldesired limit. According to one approach, the flowchart of method 1000may return to operation 1002, e.g., until another value IntegRevAve isreceived. Moreover, in other approaches, if the absolute value of theintegrator center value IntegCtr is smaller than the second thresholdthreshold2, a data entry may be made to a lookup table, a signal may besent to a system administrator, etc., e.g., by a controller that may befacilitating one or more operations of method 1000.

However, if the absolute value of the integrator center value IntegCtris greater than the second threshold threshold2, the method 1000proceeds to decision 1016. Decision 1016 determines whether a variableMovingstep is set to true TRUE, e.g., a value corresponding to acondition. If Movingstep is not set to true TRUE, method 1000 moves tooperation 1018 where a target step Target_step is calculated.

As shown in operation 1018, the target step Target_step value is equalto the current position of the coarse actuator Current_step added toIntegCtr/145. As described above, the operations in this examplecorrespond to a stepper motor which changes the position of the magnetichead by 145 counts for each step, but may be adapted and executed insimilar fashion to embodiments using any number of counts per step.Thus, in the present example, IntegCtr/145 represents the number ofsteps it would take the coarse actuator to substantially align themagnetic head with a given target track. However, in other embodiments,each step performed by the coarse actuator may correspond to a differentnumber of counts. Thus, in such other embodiments, the target step maybe calculated by incorporating the number of counts corresponding toeach step of the coarse actuator. For example, if a stepper motorchanges the position of the magnetic head by 100 counts for each step,Target_step would be equal to Current_step added to IntegCtr/100.

With continued reference to operation 1018, once the target stepTarget_step is calculated, Movingstep is set to true TRUE, wherebymethod 1000 proceeds to decision 1020. Decision 1020 determines whetherthe current position of the coarse actuator Current_step is equal to thetarget step Target_step. If Current_step is equal to the target stepTarget_step, the current position of the coarse actuator is at thetarget location. Thus, according to one approach, the flowchart ofmethod 1000 may return to operation 1002, e.g., until another valueIntegRevAve is received.

However, if decision 1020 determines that Current_step is not equal tothe target step Target_step, the method proceeds to decision 1022 wherethe integrator center value IntegCtr is compared to zero. If IntegCtr isgreater than zero, the current position of the magnetic headCurrent_step is decremented 1 step. See operation 1024. However, ifIntegCtr is less than zero, the current position of the magnetic headCurrent_step is incremented 1 step. See operation 1026.

By decrementing or incrementing the current position of the magnetichead as seen in operations 1024, 1026 respectively, the magnetic head ispreferably moved towards the target step. Moreover, method 1000 returnsto decision 1020 where the current position of the coarse actuatorCurrent_step is again compared to the target step Target_step. IfCurrent_step is still not equal to Target_step, method 1000 proceeds todecision 1022 as described above. However, if Current_step is equal toTarget_step, method 1000 moves to operation 1028 where IntegTop,IntegBot and IntegCtr are set to zero, and the flowchart is reset, e.g.,returns to operation 1002.

Referring now to FIGS. 11A-11C, the graphs 1100, 1110, 1120 depictedtherein illustrate the exemplary effects achieved by implementing theprocess steps of methods 900 and 1000 on data corresponding to LTMphenomena for different tapes and/or cartridges. Specifically, thegraphs 1100, 1110, 1120 of FIGS. 11A-11C illustrate the results that theinventors achieved by implementing the methods of FIGS. 9 and 10 on thedifferent LTM phenomena illustrated in FIGS. 8A-8C respectively, and asdescribed above.

Similar to the graphs illustrated in FIGS. 8A-8C, the x-axis of thegraphs 1100, 1110, 1120 in FIGS. 11A-11C represents a number of cyclescorresponding to sampling intervals used to collect the data presentedtherein. In the examples shown, the sampling interval is 50microseconds. Thus, the sampling intervals of graphs 1100, 1110, 1120may be translated into units of time by multiplying by 50 microseconds(μsec). For example, the sampling interval 2×10^4, corresponds to (50μsec)×(2×10^4)=1.0 second.

Looking to the graph 1100 of FIG. 11A, IntegRevAve remains at anapproximately constant value between −1000 and −1500 on the x-axis.Thus, referring back to the method 900 of FIG. 9, decision 908 willrepeatedly result in a NO because IntegRevAve will not be greater thanzero. The method thereby proceeds to operation 912 to calculateIntegBot, rather than operation 910 to calculate IntegTop. As a result,decision 914 will also repeatedly result in a NO as IntegTop will not becalculated. It follows that IntegCtr will not be updated (e.g., changed)from its value of zero which is represented in the graph 1100.

Moreover, looking now to method 1000 of FIG. 10, decision 1004 willrepeatedly result in a NO as the absolute value of IntegRevAve (which isbetween 1000 and 1500 for the present embodiment, as previouslymentioned) is continually less than threshold1 which was set at 3000 forthe present embodiment. Moving to decision 1014, the absolute value ofIntegCtr (which decision 914 of method 900 determined would remain atzero) is continually less than threshold2 which was set at 500 for thepresent embodiment. As a result, the current position of the magnetichead Current_step is not incremented or decremented, and remains atabout 550 as shown in graph 1100.

Referring now to graph 1110 of FIG. 11B, the Current_step is fixed forportions of the graph for which the IntegRevAve value is about constantbetween 1000 and 2000 on the x-axis. However, Current_step isdecremented corresponding to the downward spikes seen in the graph 1110.Looking to the method 1000 of FIG. 10, during the downward spikes,IntegRevAve reaches almost −3500, thereby resulting in the absolutevalue of IntegRevAve being less than threshold1 and causing method 1000to proceed to decision 1006 from decision 1004. Moreover, decision 1006results in a NO thereby moving to operation 1008 where Current_step isdecremented by one step as seen in graph 1110.

Both of the exemplary embodiments depicted in FIGS. 11A and 11B dealwith a signal corresponding to a phenomenon in which tape primarilyremains laterally shifted from a magnetic head in one direction, e.g.,resulting from a flange shift as described above. Although theembodiment of FIG. 11B includes short downward stack shifts, for thephenomenon shown in both FIGS. 11A and 11B, the position of the coarseactuator is preferably updated once per revolution of the supply reel.

However, moving to FIG. 11C, if an embodiment includes a signalcorresponding to a phenomenon in which the tape is laterally shiftedfrom a magnetic head in a mixture of both directions, the position ofthe coarse actuator is preferably updated more frequently than once perrevolution of the supply reel. For example, as described above, if atape supply reel has 24 portions corresponding to each full revolutionthereof, the position of the coarse actuator may be updated for each ofthe 24 portions of the full revolution of the supply reel.

Looking to graph 1120 of FIG. 11C, the data plotted thereon isconsistent with a phenomenon in which the tape alternates between beinglaterally shifted to one side of the magnetic head and being laterallyshifted to the opposite side of the magnetic head. Following the datapoints representing the current location of the coarse actuatorCurrent_step, there are two main locations at which Current_step isdecremented.

Looking to the first location, Current_step is decremented by two stepsfrom about 3300 to about 2800 along the y-axis of graph 1120. Thisdecrement corresponds to the sharp downward spike of IntegRevAvereaching below −3000. As described above with reference to FIG. 11B, thedownward spike of IntegRevAve below −3000 causes decision 1006 of method1000 to result in a NO thereby moving to the method 1000 to operation1008 where Current_step is decremented by one step. This process is thenrepeated to result in the second decremented step of Current_step.

Furthermore, looking to the second location, Current_step is decrementedby one step from about 2800 to about 2550 along the y-axis of graph1120. This decrement corresponds to the sharp downward spike ofIntegRevAve reaching almost −3000. Moreover, this downward spike ofIntegRevAve causes IntegCtr to drop from zero to less than −500.

Referring back to decision 1004 of FIG. 10, because the absolute valueof IntegRevAve is not greater than the first threshold value threshold1,which was set at 3000 for the present tested embodiment, the flowchartof method 1000 moves to decision 1014. Here it is determined that theabsolute value of IntegCtr is greater than the second thresholdthreshold2, which was set at 500 for the present tested embodiment.Thus, decision 1014 results in a YES, whereby the flowchart proceeds toeventually increment Current_step in operation 1026 resulting frommethod 1000 determining that decision 1022 is not satisfied, producing aNO.

As a result, IntegCtr was incremented, causing the absolute value ofIntegCtr to become smaller than threshold2. Moreover, the overallIntegRevAve was better centered towards zero on the y-axis, therebycorresponding to a lowered overall offset of the tape relative to themagnetic head of the present embodiment.

Thus the various embodiments described herein present a coarse servoalgorithm which is able to better position the coarse actuator for avariety of phenomena for different tapes and/or cartridges, e.g., toimprove reading and/or writing performed by an exemplary head on thedifferent tapes and/or cartridges, depending on the desired embodiment.

It will be clear that the various features of the foregoing systemsand/or methodologies may be combined in any way, creating a plurality ofcombinations from the descriptions presented above.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

According to an exemplary embodiment, which is in no way intended tolimit the invention, a computer program product may include a computerreadable storage medium having program code embodied therewith.Moreover, the program code may be readable/executable by a controller(e.g., see 128 of FIG. 1A) to perform one or more of the operations ofmethod 900 and/or 1000 illustrated in FIGS. 9 and 10 respectively.

Furthermore, in other embodiments, a computer program product mayinclude a computer readable storage medium having program instructionsstored/encoded thereon. Moreover, the program instructions may beexecutable by a controller to cause the controller to perform one ormore of the operations of method 900 and/or 1000 illustrated in FIGS. 9and 10 respectively.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider).

Aspects of the present invention are described below with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

Moreover, a system according to various embodiments may include aprocessor and logic integrated with and/or executable by the processor,the logic being configured to perform one or more of the process stepsrecited herein. By integrated with, what is meant is that the processorhas logic embedded therewith as hardware logic, such as an applicationspecific integrated circuit (ASIC), a field programmable gate array(FPGA), etc. By executable by the processor, what is meant is that thelogic is hardware logic, software logic such as firmware, operatingsystem, etc., or some combination of hardware and software logic that isaccessible by the processor and configured to cause the processor toperform some functionality upon execution by the processor. Softwarelogic may be stored on local and/or remote memory of any memory type, asknown in the art. Any processor known in the art may be used, such as asoftware processor module and/or a hardware processor such as an ASIC, aFPGA, a central processing unit (CPU), an integrated circuit (IC), etc.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

It will be further appreciated that embodiments of the present inventionmay be provided in the form of a service deployed on behalf of acustomer.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of an embodiment of the presentinvention should not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the followingclaims and their equivalents.

What is claimed is:
 1. A computer program product for positioning anactuator, the computer program product comprising a computer readablestorage medium having program instructions embodied therewith, whereinthe computer readable storage medium is not a transitory signal per se,the program instructions executable by a processing circuit to cause theprocessing circuit to perform a method comprising: generating orreceiving, by the processing circuit, a first value representative of alateral position of a tape; using, by the processing circuit, the firstvalue to adjust a position of a coarse actuator for moving a magnetichead in response to determining that the first value is in a first rangerelative to a first threshold; and using, by the processing circuit, anintegrator value to adjust the position of the coarse actuator inresponse to determining that the first value is in a second rangerelative to the first threshold.
 2. The computer program product asrecited in claim 1, wherein the integrator value is calculated using thefirst value.
 3. The computer program product as recited in claim 1,wherein the first value is updated after each revolution of a supplyreel.
 4. The computer program product as recited in claim 1, whereinusing the integrator value to adjust the position of the coarse actuatorcomprises calculating a target step based on the integrator value. 5.The computer program product as recited in claim 1, wherein theintegrator value is calculated using the first value and a second value,the value corresponding to the tape being positioned toward a firstflange of a supply reel, the second value being previously stored andcorresponding to the tape being positioned toward a second flange of thesupply reel opposite the first flange.
 6. The computer program productas recited in claim 1, comprising program instructions executable by theprocessing circuit to cause the processing circuit to compare theintegrator value to a second threshold, and determine whether or not toadjust the position of the coarse actuator based on the comparing of theintegrator value to a second threshold.
 7. The computer program productas recited in claim 1, wherein adjusting the position of the coarseactuator moves a magnetic head relative to a tape.
 8. An apparatus,comprising: a magnetic head; the computer readable storage medium ofclaim 1; a processing circuit for executing the program instructionsstored on the computer readable storage medium; and a drive mechanismfor passing a magnetic data storage medium over the magnetic head.